Mercury switch



April 16,- 1929. W, R ARMSRONG 1,708,996

MERCURY SWITCH Filed April 6, 1928 Patented Apr.'` 16, 1929.,

WALTER R. ARMSTRONG, OF CHICAGO,

ILLINOIS, ASSIG-NOR OF ONE-HALF TO FRANKLIN MAYO, OF CHICAGO, ILLINOIS.

MERCURY SWITCH.

Application filed April 6, 1928.

My invention relates to mercury Switches of the kind wherein a quantityof mercury within ra tilting tube acts to establish and break a circuithaving its conductors terminating in the tube.

Tilting mercury switches which have been known and used for many yearshave been of two general types, namely those wherein opening and closingof a circuit is effected by the separation and coming together ofportions of a body of mercury, and those wherein the mercury does notseparate but, in its movements, engages and disengages with one f a pairof fixed electrodes to establish and break a conducting path between apair of such electrodes.

All of these mercury switches with which we have heretofore beenfamiliar have been subject to certain serious objections when utilizedto interrupt the flow of currents of any considerable amperestrength,-objec tions which have come to be regarded as inherent andunavoidable in this kind of switch.

The impingement of recurring arcs upon the glass or other material ofthetube detaches small particles of the tube material at or adjacent thepoint wherein the arcing occurs and eventually causes disruption of thetube. Moreover, the co-mingling of the detached particles of the tubematerial with the mercury tends to make the action of the latter moresluggish than is desirable. Fitting of the tube by arcing alsooftentimes impairs .the performance of the mercury. Furthermore,

the continuous occurrence of substantial arcs in the mercury switch hasan objectionable effect upon the mercury, making its flow sluggish andcausing the mercury and /or impurities therein contained to give offgases which cloud the tube, which preferably should be transparent.

The disadvantages just mentioned are practic-ally eliminated by thepresent invention, two characteristic embodiments of which areillustrated in the accompanying drawing.

In the drawing: l.

Figure l is a longitudinal section of a switch tube and its associatedparts constructed and arranged in accordance with my presling andtilting mechanism being omitted, and the circuit connections beingdiagrammatically illustrated; and

Figure 2 is a similar view illustrating a modified embodiment of theinvention, where- `ent invention,-the conventional tube hold-- SerialNo. 267,857.

in the reduction and interruption of the eurrent flow is effected by theactual disengagement of the mercury from fixed electrodes, asdistinguished from the arrangement of Figure 1, wherein the reductionand interruption of the current flow is accomplished by separation ofthe mercury into disconnected portions.

Referring to the drawings, the switch tube, preferably formed of glass,is illustrated at 3, this tube containing a quantity of mercury 4l andalso preferably containing one of the gases found suitable for use inthese tilting mercury switches, for instance, hydrogen. Ordinarily, asis well understood in the art, these tubes are supported upon a tiltingmechanism (not shown), whichv in turn is acted upon by a suitablecontrolling or operating mechanism to tilt the tube when the circuitcontrolled by the switch is to be completed or broken. For the purposesof the present description, it may be assumed that the tube moves in avertical plane around the axis or fulcrum F, tion of the feathered arrowA when the circuit is to be opened, and being tilted in the being tiltedin the diree.

direction of the unfeathered arrow B when the circuit is to be closed.

The tube shown in Figure 1 is provided with three depressions or wells5, 6 and 7 a certain portion of the mercury always remaining in each ofthese wells. Ordinarily, the tube 3 will be tilted in the direction ofthe feathered arrow A sufliciently to vcause the main body of mercury 4successively to separate itself from the mercury contained in the wells5 and 6, but not necessarily sufficiently to cause a separation of themain body of mercury from the portion contained in the well 7. Thus, forthe purpose of the specifi cation and the appended claims, mercuryportions which always remain in the wells 5 and 6 may be regarded asmercury electrodes from which the main body of mercury 4 is detached andwith which the said main body of mercury is caused to hereinafterexplained.

The wells', 6 and 7 are conveniently located in bosses or enlargedportions of the tube wall, as illustrated. Entering each of theseenlarged portions is a lead in wire 8. conveniently of copper, the'inner end of which is connected in the usual manner with a suitablemetal alloy 9, which is imbedded in the glass and has substantially thesame join for the purposes coefficient of expansion as the glass. Fromeach of the elements 9 extends a short conductor 10, which is at alltimes in electrical contact with the mercury portion contained in thewell into which it projects. rl`he conductors 10 are preferably formedof iron or other material which will not become amalgamated withmercury. lVhenever the conductors 10 are not formed of iron, theportions thereof, which otherwise would be eX- posed to Contact with themercury, may be protected by small sleeves 1l of iron, carbon or thelike. The sleeves 11 also serve the purpose otl increasing the surfacecontact between the mercury and the conductors projertiug into thewells.

At C and C are indicatedl the conductors of a circuit controlled by myimproved switch, the conductor C being at all times connected with themercury electrode 8, and the conductor C being at all times connectedwith the mercury electrode 5. Mercury electrode G is at all timesconnected through a relatively high resistance 12 with the mercuryelectrode 5.

It will be understood without illustration that the conductorsconnecting with the lead in wires 8 will be sufficiently flexible toper- -mit ready tilt-ing of the tube, and that the resistance winding 12will preefrably, .but not necessarily, be mounted at some convenientpoint upon the tube holding and tilting mechanism.

With the tube in the position shown in Figure 1, the circuit controlledby the switch will be closed without encountering any appreciableresistance in the switch. Upon tilting of the tube in the direction ofthe arrow A, the main body of mercury will move toward the lower end ofthe tube, the first result of this movement being a physical separationof the main body of mercury from that which always occupies the well 5.This separation of the mercury electrode in the well 5 from the vmainbody of mercury is not accompanied by any arc, or any substantial arc,due to the continuance of current How through the high resistance path,including the resistance 12. Ordinarily the coil or winding 12 will havesuch resistance as to reduce the current .iiow by eighty or ninetypercent immediately following the interruption of the low resist-ancepath through the switch. Almost immediately following the interruptionof the low resistance path, the high resistance path, including thewinding 12, will be interrupted by the separation of the main body ofmercury from the mercury always occupying the well 6, but in thisinstance there will be vno are, or any appreciable arc, due to the factthat the current now flowing is an extremely small part of the normalcurrent flow. The circuit controlled by the switch is now opened. Onreverse tilting of the tube, in the direction of the arrow B, thecircuit controlled by the switch is lirst closed through the resistancewinding 12, and is then almost immediately given a low resistance patharound the resistance 12, when the main body of mercury joins themercury contained in the well 5.

rI`he embodiment of my invention illustrated in Figure 2 requires noparticular comment, except perhaps to say that in this instance theelectrodes 5, G and 7 are fixed electrodes, preferably of iron, withwhich the mercury 4 makes and breaks contact when the tube is tilted toand fro.

Either of the constructions illustrated in the accompanying drawingswill eliminate and/or minimize all of the hereinbefore mentionedobjections of the two electrode mercury switches of the prior art. Ibelieve I am the first to suggest providing a tilting mercury switchwith a multiplicity of electrodes and/or a resistance for the purposesherein set forth.

- I-Iaving thus described two practical embodiments of my invention, Ido not limit myself to the particular constructions here in set forth,but wish to cover all the equivalent constructions falling wit-hin theterms and spirit of the appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. A mercury switch comprising a tube tiltable about a fulorum, aquantity of mercury in said tube, three spaced electrodes extending intosaid tube through one end thereof and terminating at different distancesfrom the fulcrum of said tube, the said electrodes valso being spacedfrom each other so that contact with the mercury is made and brokenserially.

2. A mercury switch comprising a tube tiltable about a fulcrum, threespaced electrodes extending into said tube through one end thereof andterminating in downturned ends spaced from each other and at differentdistances from the fulcrum of the tube whereby contact will be made andbroken serially.

In witness whereof, I hereunto subscribe my name this 3rd day of April,1928.

WALTER R. ARMSTRONG.

